Liquid crystal display having electrodes with apertures wherein the apertures have different shapes

ABSTRACT

A tetragonal ring shape aperture is formed in the common electrode on one substrate and a cross shape aperture is formed at the position corresponding to the center of the tetragonal ring shape aperture in the pixel electrode on the other substrate. A liquid crystal layer between two electrodes are divided to four domains where the directors of the liquid crystal layer have different angles when a voltage is applied to the electrodes. The directors in adjacent domains make a right angle. The tetragonal ring shape aperture is broken at midpoint of each side of the tetragon, and the width of the aperture decreases as goes from the bent point to the edge. Wide viewing angle is obtained by four domains where the directors of the liquid crystal layer indicate different directions, disclination is removed and luminance increases.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a liquid crystal display having wideviewing angle.

(b) Description of the Related Art

A liquid crystal display (LCD) includes two substrates and a liquidcrystal layer interposed therebetween. The transmittance of the incidentlight is controlled by the strength of the electric field applied to theliquid crystal layer.

A vertically aligned twisted nematic (VATN) liquid crystal display has acouple of transparent substrates which have transparent electrodes ontheir inner surfaces and a couple of polarizers attached to their outersurfaces. The VATN LCD further includes a liquid crystal layer betweenthe two substrates, and the liquid crystal layer has chirality andnegative dielectric anisotropy.

In the off state of the LCD, i.e., in the state that no voltage isapplied to the electrodes, the long axes of the liquid crystal moleculesare aligned perpendicular to the substrates.

When the sufficient voltage difference is applied to the electrodes, anelectric field perpendicular to the substrates and the liquid crystalmolecules are rearranged. That is, the long axes of the liquid crystalmolecules tilt in a direction perpendicular to the field direction orparallel to the substrates due to the dielectric anisotropy, and twistspirally with a pitch due to the chirality.

As described above, since the long axes of the liquid crystal moleculesin the off state is perpendicular to the substrates, the VATN LCD havingcrossed polarizers may have sufficiently dark state. Therefore, thecontrast ratio of the VATN LCD is relatively high compared with theconventional TN LCD. However, the viewing angle of the VATN LCD may notbe so wide due to the difference in retardation values among viewingdirections.

To overcome the above-described problem, multi-domain structures formedby varying rubbing directions in the alignment layers or by formingapertures in the transparent electrodes are proposed. Clere disclosed astructure having linear apertures in a transparent electrode in U.S.Pat. No. 5,136,407, and Hirose et al. disclosed an LCD using fringefields to make the long axes of the liquid crystal molecules to bealigned in a direction between polarizing directions in U.S. Pat. No.5,229,873. On the other hand, Lien proposed a structure having X-shapedapertures in a transparent electrode in U.S. Pat. No. 5,309,264, andHistake et al. disclosed a structure having apertures in both of theelectrodes in U.S. Pat. No. 5,434,690.

However, the proposed structures may not have a sufficiently wideviewing angle and the luminance in their on states is not so high.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to widen the viewingangle of an LCD.

It is another object of the present invention to reduce the disclinationof an LCD.

These and other objects, features and advantages are provided, accordingto the present invention, by forming apertures in field generatingelectrodes.

In detail, a liquid crystal display according to the present inventionincludes a first and a second substrate facing each other and a firstand a second electrodes on inner surfaces of the first and the secondsubstrates respectively. The first and the second electrodes face eachother, and have a plurality of first apertures and a plurality of secondapertures, respectively.

According to an aspect of the present invention, the first and thesecond apertures form a substantially closed area.

According to another aspect of the present invention, the boundaries ofthe first and the second apertures are linear, curved or bent with anobtuse angle.

According to another aspect of the present invention, the width of thefirst and the second apertures becomes larger as goes from the ends tothe center.

According to another aspect of the present invention, the width of thefirst and the second apertures are 3-20 μm.

According to another aspect of the present invention, the distancebetween the first and the second apertures are 5-20 μm.

The liquid crystal display according to the present invention mayinclude a liquid crystal layer between the first and the secondsubstrates, a first and a second alignment layers on the first and thesecond electrodes, respectively, and a first and a second polarizersattached on the outer surfaces of the first and the second substrates,respectively. The liquid crystal layer has negative dielectricanisotropy, and the first and the second alignment layer force the longaxes of the liquid crystal molecules to align perpendicular to the firstand the second substrates. The polarizing directions of the first andthe second polarizers are preferably perpendicular to each other. It ispreferable that the number of the average directions of the long axes ofthe liquid crystal molecules in the domains defined by the first and thesecond apertures are four. Preferably, the average directions make45°±10° with the polarizing directions of the first and the secondpolarizers, and the average directions of the adjacent domains aresubstantially perpendicular to each other.

The shape of the first and the second electrodes according to thepresent invention makes the liquid crystal layer therebetween to bedivided into four regions having different average directions of thelong axes, thereby causing wide viewing angle. In addition, disclinationdue to the disorder of the liquid crystal molecules is reduced byadjusting the widths and shapes of the apertures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic diagrams of a VATN LCD according to anembodiment of the present invention, respectively in black state andwhite state.

FIG. 2 is a schematic sectional view of a VATN LCD according to anembodiment of the present invention

FIG. 3 is a layout view of apertures in electrodes of a VATN LCDaccording to the first embodiment of the present invention.

FIG. 4 is a sectional view of a liquid crystal display taken along theline IV—IV in FIG. 3.

FIG. 5 is a layout view of apertures in electrodes of a VATN LCDaccording to the second embodiment of the present invention.

FIG. 6 is a layout view of apertures in electrodes of a VATN LCDaccording to the third embodiment of the present invention.

FIG. 7 is a sectional view of a liquid crystal display taken along theline IV—IV in FIG. 6.

FIGS. 8 and 9 are layout views of apertures in electrodes of VATN LCDsaccording to the fourth and fifth embodiments of the present invention.

FIG. 10 is a sectional view of a liquid crystal display according to anembodiment of the present invention.

FIGS. 11 to 15 are layout views of apertures in electrodes of VATN LCDsaccording to the sixth to tenth embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the present invention are shown. This invention may, however, beembodied in different forms and should not be construed as limited tothe embodiments set forth herein. Rather, these embodiments are providedso that this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. In thedrawings, the thickness of layers and regions are exaggerated forclarity.

FIGS. 1A and 1B are schematic diagrams of a VATN LCD according to anembodiment of the present invention, respectively in black state andwhite state.

As shown in FIGS. 1A and 1B, two glass or quartz insulating substrates10 and 20 faces each other with being spaced apart from each other.Field generating electrodes 11 and 21 made of a transparent conductivematerial such as ITO (indium tin oxide) or the like are formed on theinner surfaces of the substrates 10 and 20, respectively, andhomeotropic alignment layers 12 and 22 are formed thereon, respectively.A liquid crystal layer 100 including a nematic liquid crystal havingnegative dielectric anisotropy is interposed between the substrates 10and 20. The liquid crystal layer 100 may have chirality or the alignmentlayers 12 and 22 may be rubbed in some directions so that the directorof the liquid crystal layer 100 twists from the one alignment layer tothe other. Polarizers 13 and 23 are attached on the outer surfaces ofthe substrates 10 and 20, respectively, and polarize the rays out of theliquid crystal layer 100 and the rays incident on the liquid crystallayer 100, respectively. The polarizing directions of the polarizers 13and 23 are perpendicular to each other. The alignment layers 12 and 22may be rubbed or not.

FIG. 1A shows the off state that there is no potential differencebetween the electrodes 11 and 21. In this case, long axes or molecularaxes of the liquid crystal molecules 110 in the liquid crystal layer 100are aligned perpendicular to the surfaces of the substrates 10 and 20due to the aligning force of the alignment layers 12 and 22.

In this state, the incident light linearly polarized by the polarizer 23attached to the lower substrate 20 passes through the liquid crystallayer 100 without changing its polarization. Then, the light is blockedby the analyzer 13 attached to the upper substrate 10 to make the LCD ina black state.

When the potential difference is applied between the two electrodes 11and 21, an electric field perpendicular to the substrates 10 and 20 aregenerated, and thus the liquid crystal molecules are rearranged.

FIG. 1B shows the on state that the sufficient electric field due to thehigh potential difference between the electrodes 11 and 21 is applied tothe liquid crystal layer 100. The molecular axes of the liquid crystalmolecules in the liquid crystal layer 100 becomes perpendicular to thefield direction or parallel to the substrates 11 and 21 due to thedielectric anisotropy. However, the molecules 110 near the surface ofthe alignment layers 12 and 22 remains in its initial state since thealigning force by the alignment layers 12 and 22 is much larger than theforce due to the dielectric anisotropy. Furthermore, the liquid crystaldirector twists spirally due to the chirality or rubbing. By adjustingthe chirality of the liquid crystal layer 100, the twist angle of theliquid crystal director from the lower substrate 10 to the uppersubstrate 20 may be made to be 90°.

The incident light linearly polarized by the polarizer 23 passes throughthe liquid crystal layer 100 and its polarization rotates by 90°according to the twist of the liquid crystal director. Therefore, thelight passes through the analyzer 13 to make the LCD in a white state.

FIG. 2 shows the schematic structure of a VATN LCD having apertures inelectrodes according to an embodiment of the present invention. Forconvenience, only substrates and electrodes are depicted and the otherelements such as alignment layers are abbreviated.

As shown in FIG. 2, field-generating electrodes 11 and 21 are formed onthe upper and the lower substrates 10 and 20, respectively, and theelectrode 21 formed on the lower substrate 20 has an aperture 200.

In absence of electric field, the long axes of the liquid crystalmolecules 110 are aligned perpendicular to the substrates 10 and 20, asshown in FIG. 1A.

If the electrodes 11 and 21 have potential difference, an electric fieldis generated. Although the field direction in most regions isperpendicular to the substrates 10 and 20, the field direction near theaperture 200 is not completely perpendicular to the substrates 10 and20, and the electric field is symmetrical with respect to the aperture200. The electric field near the aperture 200 is called the fringefield. The long axes of the liquid crystal molecules are notperpendicular to the substrates 10 and 20 and make some angle. Thearrangement of the liquid crystal molecules are almost symmetrical withrespect to the aperture 200 and the liquid crystal molecules in oppositeregions with respect to the aperture 200 are arranged in oppositemanner, thereby causing wide viewing angle.

The strength of the fringe field is large near the aperture and becomessmaller as goes far from the aperture. Accordingly, if the distancebetween the apertures is properly adjusted, the liquid crystal moleculeslocated between the apertures are sufficiently affected by the fringefield. The liquid crystal layer is divided into several regions ordomains defined by the apertures, and the average axial direction, whichmeans the average direction of the long axes of the liquid crystalmolecules, in each domain varies according to the shapes and arrangementof the apertures.

Since the aperture 200 is formed when a conductive layer is patterned toform the electrode 21 by using photolithography, no separate step forforming the aperture 20 is required, and thus it is very easy to obtaina multi-domain LCD compared with other methods using such as rubbing. Inaddition, the locations and the shapes of the domains can be finelyadjustable because of the use of the photolithography. In the meantime,a plurality of wires (not shown) for supplying signals to the electrode21 may be provided on the lower substrate 20. In this case, portions ofthe electrode 11 on the upper substrate 10 located at the positioncorresponding to wires on the lower substrate 20 may be removed in orderto reduce the parasitic capacitance between the electrode 11 and thewires.

As described above, the apertures 200 may have various shapes andarrangements, and the apertures may be formed in both electrodes oreither of the electrodes. Since the shapes and arrangements of theapertures affects the average axial directions of the domains andcharacteristics such as luminance, response time and afterimages, etc.,of the LCD panels, they should be properly designed.

The aperture pattern for a multi-domain LCD according to the presentinvention satisfies the following conditions:

First, it is preferable that the number of the domains which havedifferent average axial directions, especially in a pixel, is at leasttwo, and more preferably four. The average axial direction of eachdomain, when viewed from the top, preferably makes 45°±10°, morepreferably 45° with the polarizing directions of the polarizersespecially when using crossed polarizers. In addition, it is preferablethat the average axial directions of the adjacent domains areperpendicular to each other.

Second, it is preferable that the apertures on the upper and the lowersubstrates form substantially closed areas and thus substantially closeddomains, when viewed from the top. It is because that the texture wherethe arrangement of the liquid crystal molecules is disordered isgenerated near the ends of the apertures, and thus the ends of theapertures are preferably closely located. Furthermore, the boundaries ofthe apertures are preferably linear, slowly curved or bent with anobtuse angle in order to make the arrangement of the liquid crystalmolecules to be uniform, thereby reducing the response time. Inparticular, when the apertures on the lower and upper substrates faceeach other and form a substantially closed area, it is preferable thatthe boundaries of the facing portions of the apertures are preferablylinear, slowly curved or bent with an obtuse angle. It is preferablethat the width of the aperture becomes larger as goes from the ends tothe center. The aperture patterns may be rectangular.

Finally, the width of the aperture and the distance between theapertures are preferably 3-20 μm and 5-20 μm. If the width of theaperture is larger than the former value or the distance between theapertures is less than the latter value, the aperture ratio is reduced,thereby reducing luminance and transmittance. On the contrary, if thewidth of the aperture is less than the former value or the distancebetween the apertures is larger than the latter value, the strength ofthe fringe field weakens, thereby increasing response time andgenerating disordered textures.

Now, considering these conditions, the first embodiment of the presentinvention will be described with reference to FIGS. 3 and 4. Although anLCD has a plurality of pixels, FIGS. 3 and 4 show a single pixel region300. In addition, only aperture patterns are illustrated in FIGS. 3 and4, and other elements such as TFTs, wires, etc., are not illustrated.

As shown in FIG. 3 and 4, a plurality of linear apertures 211, 212, 216and 217 are formed in a rectangular pixel region 300. A plurality offirst and second apertures 211 and 212 extending in longitudinal andtransverse directions respectively are formed in an electrode 11 on anupper substrate 10, and a cross-shaped aperture 216 and 217 includingfirst and second portions 216 and 217 extending in longitudinal andtransverse directions respectively are formed in an electrode 21 on alower substrate 20.

The first and the second apertures 211 and 212 are separated from eachother, arranged in the longitudinal direction, and form four largesquares which is substantially closed.

The first portion 216 of the lower aperture passes through the center ofthe pixel 300 in the longitudinal direction, and thus through the centerof the large squares formed by the first and the second apertures 211and 212, and both ends of the first portion 216 approaches the secondapertures 212. The plurality of second portions 217 passes through thecenter of the large squares in the transverse direction, and both endsof the second portion 217 approaches the first apertures 211.

As a result, the apertures 211, 212, 216 and 217 form small squareswhich define domains, and two edges of the small square is two apertures211 and 212 on the upper substrate 10, while the other two edges of thesmall square is two apertures 216 and 217 on the lower substrate 20.

The arrangement of the liquid crystal molecules is described withreference to FIG. 4.

As shown in FIG. 4, the liquid crystal molecules incline due to thefringe field near the apertures. The adjacent apertures 211 and 216 onthe different substrates 10 and 20 result in a fringe field which forcesthe liquid crystal molecules between the apertures 211 and 216 to alignin the same direction, i.e., the direction from the aperture 216 to theaperture 211. Accordingly, the tilt directions of the liquid crystalmolecules in the opposing regions with respect to the apertures aredifferent.

In the meantime, since the adjacent apertures defining a domain areperpendicular to each other, the director of the liquid crystal layervaries in accordance with position. However, the average axial directionin a square domain becomes the direction from the intersection of thefirst and the second portions 216 and 217 to the intersection of theextensions of the first and the second apertures. That is, the averageaxial direction in a square domain is the direction from the center tothe corner of the large square formed by the first and the secondapertures 211 and 212. This arrangement of the aperture makes sixteensquare domains in a pixel, and the average axial direction of eachdomain is one of four directions. The average axial directions of theadjacent domains are perpendicular to each other when viewed from thetop.

When the polarizing directions P1 and P2 of the polarizers are alignedin the transverse and the longitudinal directions respectively, thepolarizing directions P1 and P2 have an angle of 45° relative to theaverage axial direction of each domain when a sufficient voltage isapplied.

In the LCDs having the aperture pattern shown in FIG. 3, the liquidcrystal molecules are rearranged by the force of the electric fieldimmediately after the voltage is applied. However, the arrangement ofthe liquid crystal molecules is slowly changed by the tendency to beparallel to each other, the characteristic that the molecules of thenematic liquid crystal have. Accordingly, it takes some time to reach astable state that the movement of the liquid crystal moleculesdisappears, thereby causing a long response time.

An aperture pattern according to the second embodiment of the presentinvention shown in FIG. 5 is similar to the aperture pattern shown inFIG. 3 except for rectangular shape of the domains instead of squareshape. That is, longitudinal apertures 221 and 226 are longer thantransverse apertures 222 and 227. Accordingly, when viewed from the top,an angle made by the average axial directions in the adjacent domains isnot exactly 90°, and an angle between the polarizing directions and theaverage axial directions is not exactly 45°. However, in this case, oneof the transverse or longitudinal directions is preferred by the liquidcrystal molecules because the long axes of the liquid crystal moleculesmake a less angle with one of the two directions than with the other.Since the rearrangement of the liquid crystal molecules quickly occurredand becomes stable, the response time is relatively shorter than the LCDshown in FIG. 3.

A liquid crystal display exhibiting less response time is now described.

FIG. 6 is a layout view of an aperture pattern of an LCD according to athird embodiment of the present invention, and FIG. 7 is a sectionalview of the LCD shown in FIG. 6 taken along the line VII—VlI.

As shown in FIGS. 6 and 7, an LCD according to the third embodiment ofthe present invention includes a lower TFT (thin film transistor) panel20 and an upper color filter panel 10. Though it is not shown in thefigures, a plurality of gate lines and data lines are formed on theinner surface of the TFT panel 20, and a pixel electrode 21 and a TFT(not shown) as a switching element are formed in a lower pixel regionsurrounded by the gate lines and data lines. On the inner surface of thecolor filter panel 10 opposite to the TFT panel 20, a black matrixpattern 14 which defines an upper pixel region corresponding to thelower pixel region in the TFT panel is formed, and a color filter 15 isformed therebetween. A passivation layer 16 covers the black matrix 14and the color filter 15, and a common electrode 11 is formed thereon. Aplurality of apertures 230, 233 and 238 are formed in the commonelectrode 11 and the pixel electrode 21, and homeotropic alignmentlayers 25 and 15 are formed on the pixel electrode 21 and the commonelectrode 11, respectively.

Polarizers 13 and 23 are attached to the outer surfaces of thesubstrates 10 and 20, respectively, and retardation films 17 and 27 areinterposed between the polarizers 13 and 23 and the substrates 10 and20, respectively. An a-plate compensation film and a c-platecompensation film may be attached to respective substrates, or twoc-plate compensation films may be attached to the both substrates 10 and20. A biaxial compensation film may be used instead of the uniaxialcompensation film, and, in this case, the biaxial compensation film maybe attached to only one substrate. The slow axis, which is the directionhaving a largest refractive index, of the a-plate or biaxialcompensation film may be parallel or perpendicular to the polarizingdirections. It is preferable that the second slow axis of the biaxialcompensation film coincides with the transmission or absorption axes ofthe polarizers.

The shapes of the apertures 230, 233 and 238 are basically similar tothose of the LCD shown in FIG. 3 according to the first embodiment. Indetail, the apertures 230 and 233 on the color filter panel 10 includeslongitudinal parts 231 and 234 and transverse parts 232 and 235extending from the center of the longitudinal parts 230 and 233 in theleft or right direction. The apertures 233 and 230 located near the leftand right edges of the pixel is symmetrically arranged with respect tothe longitudinal central line of the pixel, and form four largerectangles (almost squares) arranged in the longitudinal direction. Theplurality of the apertures 238 on the TFT panel 20 have cross shapesincluding transverse parts 237 and longitudinal parts 236 crossing eachother, and the centers of the apertures 238 are located at the center ofthe large rectangles.

It is preferable that the ends of the apertures 230, 233 and 238 on thesubstrates 10 and 20 are as close as possible such that the domaindefined by the apertures 230, 233 and 238 form a substantially closedarea when viewed from the top.

The width of the apertures 230, 233 and 238 is largest at the center,and decreases as goes to the ends. Therefore, the boundaries of theapertures 230, 233 and 238 are bent with obtuse angle, and the anglemade by two apertures on the different substrates are acute angle whenviewed from the top. As a result, the domain defined by the apertures230, 233 and 238 has the diagonal substantially perpendicular to theaverage axial direction which is longer than the diagonal substantiallyparallel to the average axial direction. The ratio of the diagonalperpendicular to the average axial direction with respect to thediagonal parallel to the average axial direction becomes larger if thewidth difference between the central portion and the end portion of theapertures 230, 233 and 238 is more enlarged at the bent point. Since theliquid crystal molecules become more uniformly aligned as the apertures230, 233 and 238 are parallel to each other, the response time becomesreduced as the ratio becomes large.

In this embodiment, the average axial directions of the adjacent domainsmakes 90 degrees, and the polarizing directions P1 and P2 of thepolarizers 13 and 23 are perpendicular to each other and makes 45degrees with the average axial direction of each domain.

According to the third embodiment, four tetragonal rings formed of theapertures exist in a unit pixel. However, the number of the rings mayvary according to the conditions such as the size of the pixel. Still,to obtain the optimum luminance, the apertures preferably form regulartetragonal rings.

The width of the apertures 230, 233 and 238 is preferably in the rangeof 3-20 μm as described above.

The distance between the central points of the apertures 230, 233 and238 on the different substrates 10 and 20, which is largest distancebetween the apertures, is in the range of 10-50 μm and more preferablyin the range of 23-30 μm. However, it depends on the size or the shapeof the pixel.

Now, a fourth embodiment of the present invention is described withreference to FIG. 8.

As shown in FIG. 8, the shape of apertures is similar to that of thethird embodiment. However, the boundaries of the apertures 230, 233 and238 are bent twice while those in the third embodiment once, when only adomain is considered. In addition, considering only a domain, the edges241 and 242 generated by the twice bending of the boundaries of theapertures 230, 233 and 238 on the different substrates 10 and 20 areparallel to each other. In other words, the central portions of theapertures 230, 233 and 238 expand to the center of the domain, thecentral portions 239 of the apertures 238 becomes square. Accordingly,the distance between the apertures 230, 233 and 238 becomes muchsmaller, and the boundaries of the apertures 230, 233 and 238 approacheslinear shape, thereby decreasing response time. However, since the areaoccupied by the apertures 230, 233 and 238 becomes larger, the apertureratio decreases.

To solve this problem, the central portion 239 of the aperture 238 onthe lower substrate 20 in the fourth embodiment becomes square ringinstead of square in the fifth embodiment as shown in FIG. 9. The crossshaped aperture 238 is divided into two portions 245 and 246 in order toprevent the isolation of the portion of the electrode surrounded by thecentral portion of the aperture 238. That is, two adjacent edges of thesquare ring is connected to each other, but disconnected to theremaining two edges. Furthermore, an aperture 247 parallel to theopposing edges of the square ring is added. As a result, two domains areadded in the square ring, and the aperture ratio increases.

In the first to the fifth embodiments of the present invention, theaperture ratio and the luminance may be improved if edge portions of theapertures 230 and 233 on the upper substrate 10 are placed outside thepixel electrode 21 as shown in FIG. 10.

The shapes of the apertures on the two substrates may be exchanged.

In order to obtain shorter response time, it is preferable that theapertures on the different substrates are parallel to each other, whichis the sixth embodiment shown in FIG. 11.

A linear aperture 252 extending longitudinally is formed in the centerof a pixel electrode on a TFT panel 20, and two linear longitudinalapertures 251 on a color filter panel 10 are located left and right tothe aperture 252, and thus the apertures on the different substrates arearranged alternately. Polarizing directions P1 and P2 are perpendicularto each other and make an angle of 45° with respect to the extension ofthe apertures 251 and 252.

In this case, since the liquid crystal molecules in a domain uniformlyincline in the same direction, i.e., the direction perpendicular to theaperture, the response time is very fast as about 30 ms. However, inthis case, only 2 average axial directions are generated, and theviewing angle is not good compared with the former embodiments.

Another aperture pattern for obtaining fast response time as well asfour average axial directions is provided in the seventh embodiment ofthe present invention shown in FIG. 12.

FIG. 12 shows two adjacent pixels 310 and 320 and an aperture patternformed thereon. Apertures 253 and 255 on the upper substrate 10 andapertures 254 and 256 extend obliquely to make an angle with thetransverse and the longitudinal directions. The apertures 253, 254, 255and 256 in a pixel 310 and 320 are parallel to each other, and theextensions of the apertures in the adjacent pixels makes an angle suchas 90 degrees. In this case, a pair of pixels yields 4 different averageaxial directions.

Polarizing directions P1 and P2 are aligned in the transverse andlongitudinal directions.

The disclination that the liquid crystal molecules are disordered may begenerated near the intersections of the pixel electrodes and theapertures 254 and 256 on the lower substrate 20, more exactly, at theportion where the apertures makes an obtuse angle with the pixelelectrode. The disclination reduces the luminance of the LCD, andafterimage may be generated since the position of the disclinationregion varies according to the applied voltage.

FIG. 13, which illustrate the eighth embodiment of the presentinvention, shows a branch 257 of the aperture 253 on the color filtersubstrate, which extends to the point where the boundary of the pixelelectrode 21 and the aperture 253 make an obtuse angle along the edgesof the pixel electrode 21. The width of the branch 257 may graduallydecrease from the connection with the apertures 253 to the ends. Thisshape decreases the disclination and increases the luminance.

According to the seventh and the eighth embodiments, two average axialdirections exist in a pixel, and four average axial directions in a pairof the pixel regions.

The various arrangement of pixels having different average axialdirections are possible, and these embodiments are shown in FIGS. 14 and15.

According to the ninth embodiment shown in FIG. 14, the pixels arrangedin the row direction has the same average axial direction, while theadjacent pixels in a column have different average axial directions. Inorder to make different average axial directions, the oblique angles ofapertures is differentiated.

On the contrary, according to the tenth embodiment shown in FIG. 15, theoblique angles of the apertures of adjacent pixels in a column aredifferent, while, in row direction, the pixels in a dot including red,green and blue pixels has the same average axial direction, and theaverage axial direction is altered by unit of dot.

According to the embodiments of the present invention, multi-domain LCDsare formed using various aperture pattern to control the arrangement ofliquid crystal molecules, therefore wide viewing angle is obtained,disclination is removed and the luminance is increased.

In the drawings and specification, there have been disclosed typicalpreferred embodiments of the invention and, although specific terms areemployed, they are used in a generic and descriptive sense only and notfor purposes of limitation, the scope of the invention being set forthin the following claims.

What is claimed is:
 1. A liquid crystal display, comprising: a firstsubstrate having an inner surface and an outer surface; a firstelectrode on the inner surface of said first substrate having aplurality of first apertures; a second substrate having an inner surfaceand an outer surface; and a second electrode on the inner surface ofsaid second substrate having a plurality of second apertures and locatedat a position corresponding to the first electrode, wherein boundariesof each of first aperture and each of the second aperture are bent at anobtuse angle and wherein a respective width of the first aperture andthe second aperture tapers from a respective center of the firstaperture and the second aperture to a respective end of the firstaperture and the second aperture.
 2. The liquid crystal display of claim1, wherein the first aperture is symmetric in shape and the secondaperture is symmetric in shape.
 3. The liquid crystal display of claim1, wherein the first aperture and the second aperture form asubstantially closed area shaped as polygon having at least four sides.4. The liquid crystal display of claim 3, wherein the substantiallyclosed area formed by the first aperture and the second aperture issymmetric in shape.
 5. The liquid crystal display of claim 3, whereinthe respective width of the first aperture and the second aperture is3-20 μm.
 6. The liquid crystal display of claim 3, wherein a distancebetween the first aperture and the second aperture is 5-20 μm.
 7. Theliquid crystal display of claim 1, wherein the respective width of thefirst aperture and the second aperture gradually decreases from 20 μm to3 μm.
 8. The liquid crystal display of claim 1, further comprising: aliquid crystal layer interposed between said first substrate and saidsecond substrate and having a negative dielectric anisotropy; a firstalignment layer on said first electrode; a second alignment layer onsaid second electrode; a first polarizer on the outer surface of saidfirst substrate; and a second polarizer on the outer surfaces of saidsecond substrate, wherein said first alignment layer and said secondalignment layer respectively align the long axes of liquid crystalmolecules in said liquid crystal layer to be perpendicular to said firstsubstrate and said second substrate.
 9. The liquid crystal display ofclaim 8, wherein a polarizing direction of said first polarizer isperpendicular to a polarizing direction of said second polarizer. 10.The liquid crystal display of claim 9, wherein the number of averageaxial directions of liquid crystal molecules in domains defined by thefirst aperture and the second aperture is four.
 11. The liquid crystaldisplay of claim 10, wherein the average axial directions of liquidcrystal molecules are at an angle of 45°±10° with the polarizingdirections of said first polarizer and said second polarizer.
 12. Theliquid crystal display of claim 11, wherein the average axial directionsof liquid crystal molecules in the domain cross at a substantially rightangle.
 13. The liquid crystal display of claim 1, wherein the boundariesof the first aperture and the second aperture are bent at least twiceper each domain defined by the first aperture and the second aperture.14. The liquid crystal display of claim 1, wherein the first apertureand the second aperture form an area that is diametrically symmetric.15. The liquid crystal display of claim 14, wherein a half of thediametrically symmetric area is trapezoidal in shape.
 16. The liquidcrystal display of claim 1, further comprising: a first polarizerattached on the outer surface of said first substrate; and acompensation film interposed between said first substrate and said firstpolarizer, wherein said compensation film is uniaxial or biaxial. 17.The liquid crystal display of claims 16, wherein said compensation filmis biaxial, and one of slow axes of said compensation film issubstantially parallel to a transmission axis of said first polarizer.18. A liquid crystal display, comprising: a first substrate having aninner surface and an outer surface; a first electrode on the innersurface of said first substrate having a plurality of first apertures; asecond substrate having an inner surface and an outer surface; and asecond electrode on the inner surface of said second substrate having aplurality of second apertures and located at a position corresponding tosaid first electrode, wherein the first aperture an the second apertureform a substantially closed area, which has a polygonal shape with atleast four sides, and wherein a respective width of the first apertureand the second aperture tapers from a respective center of the firstaperture and the second aperture to a respective end of the firstaperture and the second aperture.
 19. The liquid crystal display ofclaim 18, wherein the respective width of the first aperture and thesecond aperture is 3-20 μm.
 20. The liquid crystal display of claim 18,wherein the respective width of the first aperture and the secondaperture gradually decreases from 20 μm to 3 μm.